Paper reel tension control



March 12, 1968 J, J. M DONALD 3,

PAPER REEL TENSION CONTROL Fild May 18, 1966 39 32 39 7 mn mu. 7

31v 5i Q I 3 35 36 O,- 73 O 15 6 77 3a v F/G./ 1:1

INVENTOR.

I John J. Mc Donald BY United States Patent Ofi ice 3,372,886 PatentedMar. 12, 1968 3,372,886 PAPER REEL TENSION CONTROL John J. McDonald,Park Ridge, N.J., assignor to R. Hoe & Co. Inc., New York, N.Y., acorporation of New York Filed May 18, 1966, Ser. No. 551,050 2 Claims.(Cl. 242-75.42)

ABSTRACT OF THE DISCLOSURE A device for controlling the tension in apaper web having a belt driven about an idler pulley and which is incontact with the periphery of a web roll. Means for exerting a force onthe idler pulley in response to reac tions of a web tension sensor andin a direction substantially parallel to the belt course leading fromthe web roll, resulting in a change in belt tension and consequently ashift in belt pitchline. This in turn causes minute variations in thespeed of thed riven belt to thereby vary the torque exerted by the belton the web roll which ultimately affects the tension of the web.

This invention relates to improvements in paper reel tension controls,such as are commonly used in supplying paper webs to web printingmachines.

It has been proposed to control web tension in response to a floatingroller or other sensor by varying the speed of drive of the tensioncontrol belts. Controls of this type are apt to be critical in theiroperation or not sufficiently sensitive and rapid in their response,depending on the particular type of variable speed drive which is usedand upon whether the paper roll drive is of a slipping type.

Accordingly, the variable speed belt controls which have been proposedhave not made sufiicient improvement to justify their use with belttensioning devices of the type shown, for example, in prior Patents2,617,610; 2,682,027; 3,217,999 and 2,344,952, and in which driven beltscarried in a movable frame are used to accelerate the new roll prior tosplicing and tension it during the major part of the time it feeds theweb to the printing machine. The conventional, and generally verysatisfactory, control method used in such devices utilizes movement ofthe belt frame, varying both wrap and tension, to regulate the torqueapplied to the. paper roll. In practice, the speed of the driving beltmay differ from that of the paper roll periphery by only a few feet perminute so that belt pulley speed control of the order of a fraction ofone percent, or even finer, is needed. Having in mind the unavoidableeccentricity of the web rolls, and consequent fluctuation of paper rollperipheral speed, conditions may occur where the direction of slipreverses, with a theoretical corresponding reversal as between thetensioning of the belt courses.

' It is an object of the present invention to provide a tension beltspeed control for paper roll reels, which is compatible with existingsystems and permits obtaining better control with little or no increasein cost or complication of equipment.

A further object is to provide a belt speed control which is useable asa substitute for existing control systems and provides both a simplercontrol, but also a better one. I

While applicable to other types of arrangement, the invention will bedescribed, for definiteness, with relation to a reel of the typedisclosed in the above-mentioned patents. In such reels, the tensioncontrol is effected by pivotally moving an idler pulley mounting aboutthe axis of another idler pulley, thereby varying both the angle of wrapon the paper roll and the belt tension. The moving idler pulley isspring-mounted so that the tension depends on several different factorsand the direction of movement for controlling tension is the same asthat for positioning the belt to follow the paper roll as it decreasesin diameter. In the present control system, the instantaneous, finecontrol of tension is achieved by minutely varying the belt speed, thevariation being achieved by varying the effective pitch line of thebelt, as by varying the tensioning force on the move-able idler, but ina direction substantially at right angles to the belt positioningadjustment.

With the foregoing objects in mind, as well as others which will appear,the invention will now first be fully described with reference to theaccompanying drawing, and the features forming the invention will thenbe pointed out in the appended claims.

In the drawing:

FIG. 1 is a schematic and diagrammatic side elevational view of a reelembodying the invention in a preferred form;

FIG. 2 is an enlarged view of part of FIG. 1, showing the tension beltarrangement and a modified control therefor; and

FIG. 3 is a diagrammatic enlarged view of the belt and drive pulley.

The reel structure generally is like that shown in the above-mentionedpatents, to which reference may be made for details of constructionwhich, in themselves, form no part of the present invention. Pedestal 1supports the shaft 3 of spider 2 having three sets of arms forsupporting paper rolls in the respective web-supply, expiring andpreparation positions A, B and C. Paper roll 4, in the position A, isshown as supplying the web W to a printing machine (not shown), the webpassing around the successive rollers 5 to 9. Roller 8 is a floatingroller, rising and falling as the tension increases and decreases.Proper tension is maintained by controlling the action of belts 11,which run around pulleys 12, 13 and 14, and engage the periphery ofpaper roll 4 for exerting regulating torque thereon. Pulley 12 issupported on a fixed shaft and driven by the press at a surface speedslightly less than that of the printing cylinders (and web W), pulley 13also rotates on a fixed axis but is idle, and idle pulley 14 is mountedfor adjustment to vary the wrap of the belts 11 on the paper roll 4 andfollow the roll as it decreases in diameter. The mounting comprises arms15 swinging about the axis of pulleys 13, the pulleys 14 being pivotallycarried at the lower ends of arms 16 which are pivotally attached toarms 15 at 17 and urged in belt tensioning direction by a tension springmeans 18 (FIG. 1).

In the construction of the said prior patents, the upper ends of springs18 are fixedly secured to arms 15, so that the spring tension and hencethe belt tension are determined by the roll diameter and the position ofarms 15, along with the angle of wrap of the belts on the paper roll.According to the present invention there is provided for the springs 18an adjustable upper end attachfollower roller 21 which runs against cam22, the rotary position of which is adjusted by the floating roller 8through means indicated symbolically at 25, and which may be mechanical,electrical or hydraulic. Roller 8, acting as the tension sensor, dropsin response to falling tension and rises in response to rising tension,effecting a corresponding angular adjustment of cam 22. Specifically,the means 25 may be .the same circuitry as shown in the above-mentionedprior patents for actuating motor M which controls the belt wrap, butapplied to rotative adjustment of the cam.

The adjustment of motor M and arms 15 moved therebymay be transferred tothe control of limit switch 27 (instead of the floating roller as in theprior arrangement), carried by an arm 15 and reading, through the belt,the position of the paper roll periphery with relation to the mountingfor the pulley 14. As shown, connections 28 from switch 27 lead to amotor relay control 30 which supplies current from power lines L-l, L2,to .the motor M through lines 29, for causing the belts 11 to follow theroll 4 as it decreases in diameter. Where the geometry permits,adjustment of arms 15 may be omitted. Where provided, it may involveonly one or two settings or may approximate a slow continuous movement,but, in either case, the adjustment of tensioning force on the idlers 14is so rapid that it is not interfered with by any positioning movementsof arms 15.

It will be noted that the movement of pulley 14 in swinging about pivot17 is practically at right angles to the movement as arms 15 areadjusted, so that the two adjustments are substantially independent.

In the modification shown in FIG. 2, there is substituted for the spring18 and cam 22, a pneumatic control comprising a pilot valve 31 adjustedby the floating roller through arm 32 and connected to valve box 33 byairlines 34, so that the supplying and exhausting of air to the cylinder36 controls the tension on the belts. Cylinder 36 is attached at 37 toan arm 15 and at 38 to the upper end of arm 16, thus exerting acontrolled tensioning force F on the pulley 14. Shop air may be suppliedthrough connections 39 for operating this equipment, as the pressuresrequired are not high.

FIG. 3 indicates schematically at r the radius of the pitch line of belt11 as it goes around pulley 12. This radius determines the linear speedof travel of the belt as it passes around the pulley while acorresponding radius about the center of paper roll 4 determines theratio between linear speed of the contacting belt surface and the linearspeed of the belt in its straight courses. It will be apparent thatshifting of belt pitchlines can disturb the action of prior reeltensions to a point where actual reversal of desired direction of driveof the belts on the paper roll can occur. In the system of the presentinvention, the shifting of pitchlines in response to tension variationis utilized to vary the torque and permits operation with little or noperceptible movement of the belt pulleys and practically instantaneousresponse to tension change at the sensor.

Assuming a web which is 60" wide and a web tension at the reel of 1 lb.per inch of width, these being reasonably typical figures, the Webexerts an average torque, under constant press speed conditions, of 60pounds multiplied by the paper roll radius, tending to accelerate thepaper roll. Belts 11 exert an opposing torque, averaging the same beltperipheral force on the paper roll, less whatever is required toovercome frictional factors and produce the slight acceleration involvedin increasing angular velocity with decreasing diameter. The differencein belt tension on the two sides of drive pulley 12 (or paper roll 4)will be approximately 60 pounds over-all, or, where two 4" belts areused, about 30 pounds per belt and 7.5 pounds per inch of belt width.The speed in the tight course will, with belting of usual type, be about0.2% higher than that in the slack course. Since the angle of wraparound drive pulley 12 is about 180, and

leather surface belts are used on a cast-iron pulley, there willordinarily be no slip, while the belts will ordinarily slip on the paperroll when operating with a normal wrap angle, such as, for example,thirty or forty-five degrees.

By adjusting cam 22, the tension in springs 18 can be varied from aboutlbs. to about 400 lbs., varying the tension in the belt courses atpulley 14 accordingly. Thus the belt tensions can be varied from 100lbs. and lbs. in the slack and tight sides, respectively, to 400 and 460lbs., respectively. The full specified range of tension adjustment maycorrespond to only about a 2.0% change in belt length, or a movement ofpulley 14 of only about an inch. Since the spring tension changesinvolved in controlling the web tension are small, the correspondingmovements of pulley 14 are hardly noticeable and produce no appreciablechange in the angle of wrap on the paper roll.

The change in belt pressure, per pound change of spring force on pulleys14-, is only a small percentage of the existing pressure on the paperroll and causes only a correspondingly small percentage change in drive(braking) torque. The change in belt pressure, however, in making acorrespondingly small percentage change in belt speed, due to shiftingof the effective belt pitch-line, may produce a very large percentagechange in the (slip) velocity between belts and paper roll. For example,if the speed of paper feed is 1000 ft./min. and the slip velocity is 1%,or 10 ft./min., a change of only /1o% in the belt speed will amount to10% of the slip speed, and also 10% of the power transmitted from beltsto paper roll. Assuming, by way of example, drive pulley diameter of sixinches and belt thickness of five-sixteenth inch, a pitchline shift of0.003 will amount to a speed change of ten percent of the slip speed.The adjustment in the tension difference, belt pressure and torquerequired to produce the indicated change in power transmitted areinstantaneous and automatic.

Change of effective pitch line radius with given change in tensiondepends upon a number of factors, and principally the following:material and diameter of driving and driven pulleys or other elements(e.g., the paper roll); belt thickness; presence or absence of slip onsurface of driver and driven elements; compressibility of belt (unitvolume) and ability of belt to flow; homogeneity of belt and location ofany comparatively inextensible layers. Once the system has beencalibrated for use with a particular type of belt, it is ordinarilynecessary only to continue to use the same belt (within usual commercialtolerances on the belt specifications).

What is claimed is:

1. A paper web roll tension control comprising an arm, driving and idlepulleys mounted on said arm, a belt supported and driven by said pulleyswith a course having a wrap angle around the periphery of a paper webroll, a floating roller for sensing tension variations in the web, avalve connected to the floating roller and actuated in response tomovement of said roller, a link connected at one end thereof to saidfloating roller and at the other end thereof to said valve forconnecting said floating roller to said valve, a pneumatic cylindermounted on said arm for exerting a regulable force on said idle pulleyin a direction substantially parallel to the belt course leading fromthe web roll to said idle pulley, a source of air connected to saidvalve by airlines for supplying air to said cylinder when actuated bysaid valve, whereby the force exerted on said idle pulley causes atensioning of the belt r'e's ulting in a shift of the belt pitchlinewhich causes a variation in the torque exerted by the belt on the webroll.

2. A paper web roll tension control comprising an arm, driving and idlepulleys mounted on said arm, a belt supported and driven by said pulleyswith a course having a wrap angle around the periphery of a paper webroll, a floating roller for sensing tension variations in the web, arotatably mounted cam its rotary position being adjusted by saidfloating roller, means connecting said floating roller to said Cam foradjusting the rotary position of said cam, a spring connected at one endto said cam and at its other end to said idle pulley for exerting aforce on said idle pulley in response to rotation of said cam in adirection substantially parallel to the belt course leading from the webroller to said idle pulley, whereby said force exerted on said idlepulley causes a tensioning of the belt resulting in a shift of the beltpitchline which causes variations in the torque exerted by the belt onthe web roll.

References Cited UNITED STATES PATENTS FRANK I. COHEN, Primary Examiner.10 N. L. MINTZ, Assistant Examiner.

